A complex way to get such temperatures is with a salt bath. Just find a salt that melts at the right temperature, heat in an appropriate vessel until it just melts, then add your SMA wire.
A much simpler way is to get a wax indicating marker (crayon) for the temperature you need. Mark the SMA, then heat with a soft flame or stove burner until the wax just melts. The change is obvious.
Temperature indicating markers (crayons) are used widely for annealing and heat treating metals. In the US, welding supply places usually have them. A supplier for knife making would also probably have them. The McMaster-Carr part number is 3261K91 ($10.12 USD).
John